In a Long Term Evolution (LTE) system, a network architecture is classified into two types: a centralized architecture and a distributed architecture. For the distributed architecture, a base station has a baseband function and a radio frequency function. For the centralized architecture, a baseband function is provided in a baseband control unit (BBU), and a radio frequency function is provided in a remote radio unit (RRU). The BBU and the RRU need to be connected by using a large-capacity transmission medium such as an optical fiber or a microwave. The two types of architectures are independent of a terminal device. To be specific, once an architecture is determined, either distributed scheduling or centralized scheduling is used for all terminal devices in a cell.
Scheduling in the distributed architecture is scheduling by each base station, and an effect of inter-cell coordination between different base stations is poor. Consequently, inter-cell interference between base stations is relatively severe, and a throughput of a terminal device at a cell edge is reduced. However, an advantage of the distributed architecture is to save a bandwidth of a transmission network. Because the BBU and the RRU are integrated, an additional transmission network (fronthaul) is not required. An advantage of the centralized architecture is desirable system performance. Because radio resources of a plurality of cells may be scheduled in a centralized manner (for example, by using a CoMP technology), the radio resources of the plurality of cells may be coordinated, to reduce interference and increase a throughput of a cell edge user. However, the BBU is separated from the RRU, and data that is processed by a physical (PHY) layer is transmitted between the BBU and the RRU. A transmission network (usually referred to as fronthaul) between the BBU and the RRU needs to transmit a large amount of data, and a bandwidth requirement is very high. Further, when a frequency bandwidth supported by a cell increases, an air interface needs to transmit more data. Correspondingly, a bandwidth requirement of a transmission network also increases, causing a high pressure on the bandwidth of the transmission network.